Well since the response before was good, I made some fighter designs, just to compare...
Morning Star class Fighter 180 tons 19 Crew 148.5 BP TCS 3.6 TH 450 EM 0
125000 km/s Armour 1-2 Shields 0-0 Sensors 7/1/0/0 Damage Control Rating 0 PPV 1
Annual Failure Rate: 36% IFR: 0.5% Maint Capacity 0 MSP Max Repair 75 MSP Est Time: 0 Years
Magazine 18
FTR Photonic Drive E200 (1) Power 450 Fuel Use 2000% Signature 450 Armour 0 Exp 175%
Fuel Capacity 10,000 Litres Range 5.0 billion km (11 hours at full power)
Size 1 Missile Launcher (1) Missile Size 1 Rate of Fire 5
Missile Fire Control FC4-R1 (1) Range 4.1m km Resolution 1
Size 1 MP AM AS Deep Spike (18) Speed: 99,000 km/s End: 0.6m Range: 3.6m km WH: 24 Size: 1 TH: 330 / 198 / 99
Thermal Sensor TH0.1-7 (10%) (1) Sensitivity 7 Detect Sig Strength 1000: 7m km
Missile to hit chances are vs targets moving at 3000 km/s, 5000 km/s and 10,000 km/s
This design is classed as a military vessel for maintenance purposes
This design is classed as a fighter for production and combat purposes
I'd put more launchers on the fighter. As it is you will be firing salvoes of a single missile which will be much easier for point defence to shoot down all of them. If you haven't got reduced size launchers yet, research them as soon as you can. Strip off the current launcher and magazine and replace with an equal tonnage of box launchers.
As has been discussed many times in this thread your warheads on your missiles could do with being increased to size 25 so as to give penetration to another armour level.
Personally I'd add
CompactSmall craft ECM and
CompactSmall craft ECCM to your design if you have them, as these can quite significantly effect your fighters survivability and ability to hit with those missiles.
I wouldn't bother putting thermal sensors on a combat fighter, as more than one in a squadron is essentially wasted space. If you want your fighter squadron to have passive sensors it is better to design a dedicated sensor fighter to accompany the combat fighters. As the above design lacks active sensors, you could add those to your sensor fighter to allow the squadron to operate outside the sensor envelope of their baseship.
edit:Just had a play around with an all tech game.
Missile fighter set up to spam size 1 missiles.
Vanguard class Fighter 500 tons 15 Crew 634 BP TCS 10 TH 4.5 EM 0
45000 km/s Armour 1-5 Shields 0-0 Sensors 1/1/0/0 Damage Control Rating 0 PPV 7.5
Annual Failure Rate: 100% IFR: 1.4% Maint Capacity 0 MSP Max Repair 300 MSP Est Time: 0 Years
Magazine 50
FTR Photonic Drive E200 (1) Power 450 Fuel Use 2000% Signature 4.5 Armour 0 Exp 175%
Fuel Capacity 10,000 Litres Range 1.8 billion km (11 hours at full power)
Size 1 Box Launcher (50) Missile Size 1 Hangar Reload 7.5 minutes MF Reload 1.2 hours
Missile Fire Control FC4-R1 (10%) (1) Range 4.1m km Resolution 1
Size 1 Fighter ASM (50) Speed: 46,500 km/s End: 1.5m Range: 4.1m km WH: 25 Size: 1 TH: 604 / 362 / 181
Small Craft ECCM-5 (1) ECM 50
Missile to hit chances are vs targets moving at 3000 km/s, 5000 km/s and 10,000 km/s
This design is classed as a military vessel for maintenance purposes
This design is classed as a fighter for production and combat purposes
The sensor-fighter to accompany each squadron.
Invincible class Fighter-Scout 500 tons 51 Crew 4102 BP TCS 10 TH 4.5 EM 0
45000 km/s Armour 1-5 Shields 0-0 Sensors 75/68/0/0 Damage Control Rating 0 PPV 0
Annual Failure Rate: 100% IFR: 1.4% Maint Capacity 0 MSP Max Repair 3240 MSP Est Time: 0 Years
FTR Photonic Drive E200 (1) Power 450 Fuel Use 2000% Signature 4.5 Armour 0 Exp 175%
Fuel Capacity 10,000 Litres Range 1.8 billion km (11 hours at full power)
Active Search Sensor MR81-R1 (10%) (1) GPS 1080 Range 81.0m km Resolution 1
Thermal Sensor TH1-75 (10%) (1) Sensitivity 75 Detect Sig Strength 1000: 75m km
EM Detection Sensor EM0.9-67.5 (10%) (1) Sensitivity 67.5 Detect Sig Strength 1000: 67.5m km
ECM 50
This design is classed as a military vessel for maintenance purposes
This design is classed as a fighter for production and combat purposes
As you've been going with smaller faster fighters heres a variant that sticks to that theme.
Illustrious class Fighter 185 tons 15 Crew 608.8 BP TCS 3.7 TH 4.5 EM 0
121621 km/s Armour 1-2 Shields 0-0 Sensors 1/1/0/0 Damage Control Rating 0 PPV 1.2
Annual Failure Rate: 37% IFR: 0.5% Maint Capacity 0 MSP Max Repair 300 MSP Est Time: 0 Years
Magazine 8
FTR Photonic Drive E200 (1) Power 450 Fuel Use 2000% Signature 4.5 Armour 0 Exp 175%
Fuel Capacity 10,000 Litres Range 4.9 billion km (11 hours at full power)
Size 1 Box Launcher (8) Missile Size 1 Hangar Reload 7.5 minutes MF Reload 1.2 hours
Missile Fire Control FC4-R1 (10%) (1) Range 4.1m km Resolution 1
Size 1 ASM Mk II (8) Speed: 121,500 km/s End: 0.6m Range: 4.1m km WH: 16 Size: 1 TH: 4009 / 2405 / 1202
Small Craft ECCM-5 (1) ECM 50
Missile to hit chances are vs targets moving at 3000 km/s, 5000 km/s and 10,000 km/s
This design is classed as a military vessel for maintenance purposes
This design is classed as a fighter for production and combat purposes
It's associated sensor-fighter.
Broadsword class Fighter-Scout 185 tons 20 Crew 1150 BP TCS 3.7 TH 4.5 EM 0
121621 km/s Armour 1-2 Shields 0-0 Sensors 30/30/0/0 Damage Control Rating 0 PPV 0
Annual Failure Rate: 37% IFR: 0.5% Maint Capacity 0 MSP Max Repair 540 MSP Est Time: 0 Years
FTR Photonic Drive E200 (1) Power 450 Fuel Use 2000% Signature 4.5 Armour 0 Exp 175%
Fuel Capacity 10,000 Litres Range 4.9 billion km (11 hours at full power)
Active Search Sensor MR13-R1 (10%) (1) GPS 180 Range 13.5m km Resolution 1
Thermal Sensor TH0.4-30 (10%) (1) Sensitivity 30 Detect Sig Strength 1000: 30m km
EM Detection Sensor EM0.4-30 (10%) (1) Sensitivity 30 Detect Sig Strength 1000: 30m km
ECM 50
This design is classed as a military vessel for maintenance purposes
This design is classed as a fighter for production and combat purposes
As you can see from comparing the two missile variants a size 25 warhead is really too big to go on a size 1 missile even at max tech. The size 16 warhead variant is both much faster as well as having a far higher chance to hit.